Method and apparatus for controlling uplink power in wireless

ABSTRACT

Descriptions on the method and the apparatus for controlling uplink transmission power are provided. The method for controlling uplink transmission power comprises receiving a signal on a downlink channel, wherein the signal includes information on transmission power which indicates a power control mode, determining whether primary cell (PCell) and secondary cell (SCell) are asynchronous or synchronous, determining maximum transmission power for the SCell, using the information on transmission power, based on whether the PCell and the SCell are asynchronous or synchronous, and transmitting signal to the SCell based on the maximum transmission power for the SCell.

TECHNICAL FIELD

The present invention relates to wireless communications, and moreparticularly, to a method and apparatus for controlling an uplink powerin a wireless communication system.

BACKGROUND ART

Universal mobile telecommunications system (UMTS) is a 3^(rd) generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). A long-term evolution (LTE) of UMTS is under discussion by the3^(rd) generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3GPP LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

To increase the capacity for the users' demand of services, increasingthe bandwidth may be essential, a carrier aggregation (CA) technology orresource aggregation over intra-node carriers or inter-node carriersaiming at obtaining an effect, as if a logically wider band is used, bygrouping a plurality of physically non-continuous bands in a frequencydomain has been developed to effectively use fragmented small bands.Individual unit carriers grouped by carrier aggregation is known as acomponent carrier (CC). For inter-node resource aggregation, for eachnode, carrier group (CG) can be established here one CG can havemultiple CCs. Each CC is defined by a single bandwidth and a centerfrequency.

In LTE Rel-12, a new study on small cell enhancement has started, wheredual connectivity is supported. Dual connectivity is an operation wherea given UE consumes radio resources provided by at least two differentnetwork points (master eNB (MeNB) and secondary eNB (SeNB)) connectedwith non-ideal backhaul while in RRC_CONNECTED. Furthermore, each eNBinvolved in dual connectivity for a UE may assume different roles. Thoseroles do not necessarily depend on the eNB's power class and can varyamong UEs.

Uplink power control determines the average power over a single carrierfrequency division multiple access (SC-FDMA) symbol in which thephysical channel is transmitted. Uplink power control controls thetransmit power of the different uplink physical channels. Efficientuplink power control method for CA or dual connectivity may be required.

SUMMARY OF INVENTION Technical Problem

The present invention provides a method and apparatus for reporting PHRefficiently depending on whether MeNB and SeNB are asynchronous orsynchronous.

The present invention provides a method and apparatus for determiningmaximum transmission power efficiently when when MeNB and SeNB areasynchronous or synchronous considering overlapped portions betweensubframes of the MeNB and subframes of the SeNB.

The present invention provides a method and apparatus for determiningmaximum transmission power of SeNB efficiently considering usedtransmission power at previous subframe of MeNB. The present inventionprovides a method and apparatus for determining MeNB and SeNB aresynchronous or asynchronous.

Technical Solution

An embodiment of the present invention is a method of controlling uplinktransmission power in wireless communication system. This method maycomprise receiving a signal on a downlink channel, wherein the signalincludes information on transmission power which indicates a powercontrol mode, determining whether primary cell (PCell) and secondarycell (SCell) are asynchronous or synchronous, determining maximumtransmission power for the SCell, using the information on transmissionpower, based on whether the PCell and the SCell are asynchronous orsynchronous, and transmitting signal to the SCell based on the maximumtransmission power for the SCell.

Another embodiment of the present invention is an apparatus forcontrolling uplink (UL) transmission power in wireless communicationsystem. This apparatus may comprise a radio frequency (RF) unit fortransmitting and receiving a radio signal, wherein the radio signalincludes information on transmission power which indicates a powercontrol mode, and a processor operatively coupled to the RF unit. Theprocessor may be configured for transmitting signals via the RF unitbased on a scheduling for UL and/or downlink (DL). The processor maydetermine whether primary cell (PCell) and secondary cell (SCell) areasynchronous or synchronous, and may determine maximum transmissionpower for SCell, using the information on transmission power, based onwhether the PCell and the SCell are asynchronous or synchronous. The RFunit may transmit radio signal to the SCell based on the maximumtransmission power for the SCell.

Advantageous Effects

According to the present invention, power headroom can be determinedefficiently depending on whether MeNB and SeNB are asynchronous orsynchronous.

According to the present invention, maximum transmission power can bedetermined efficiently considering overlapped portions between subframesof the MeNB and subframes of the SeNB or considering used transmissionpower at previous subframe of MeNB.

According to the present invention, it is determined efficiently whetherMeNB and SeNB are synchronous or asynchronous and parameter values forthe transmission power can be determined using whether MeNB and SeNB aresynchronous or asynchronous.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows structure of a radio frame of 3GPP LTE.

FIG. 3 shows a resource grid for one downlink slot.

FIG. 4 shows structure of a downlink subframe.

FIG. 5 shows structure of an uplink subframe.

FIG. 6 shows an example of a carrier aggregation of 3GPP LTE-A.

FIG. 7 shows an example of dual connectivity to a macro cell and a smallcell.

FIG. 8 briefly describes an example of obtaining maximum powerconsidering the overlapped subframes according to the presentinvention(s).

FIG. 9 briefly describes an example of power scaling according to thepresent invention(s).

FIG. 10 describes an example of determining PCMAX in asynchronous case.

FIG. 11 briefly illustrates a case that PUCCH at (n+1)-th subframe onMeNB and PUCCH at n-th subframe on SeNB are overlapped.

FIG. 12 briefly shows another example of a case that PUCCH and PRACHcollide.

FIG. 13 briefly shows an example of an asynchronous case between MeNBand SeNB.

FIG. 14 briefly describes behavior of determining PCMAX.

FIG. 15 briefly describes an example of handling limitation on the powerconsidering power used in previous subframe.

FIG. 16 is a flow chart briefly describing an example as for anoperation of the UE according to the present invention(s) in thisdisclosure.

FIG. 17 is a block diagram which briefly describes a wirelesscommunication system including an UE and a BS.

MODE FOR INVENTION

Techniques, apparatus and systems described herein may be used invarious wireless access technologies such as code division multipleaccess (CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), orthogonal frequency division multiple access(OFDMA), single carrier frequency division multiple access (SC-FDMA),etc. The CDMA may be implemented with a radio technology such asuniversal terrestrial radio access (UTRA) or CDMA2000. The TDMA may beimplemented with a radio technology such as global system for mobilecommunications (GSM)/general packet radio service (GPRS)/enhanced datarates for GSM evolution (EDGE). The OFDMA may be implemented with aradio technology such as institute of electrical and electronicsengineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20,evolved-UTRA (E-UTRA) etc. The UTRA is a part of a universal mobiletelecommunication system (UMTS). 3rd generation partnership project(3GPP) long term evolution (LTE) is a part of an evolved-UMTS (E-UMTS)using the E-UTRA. The 3GPP LTE employs the OFDMA in downlink and employsthe SC-FDMA in uplink. LTE-advance (LTE-A) is an evolution of the 3GPPLTE. For clarity, this application focuses on the 3GPP LTE/LTE-A.However, technical features of the present invention are not limitedthereto.

FIG. 1 shows a wireless communication system. The wireless communicationsystem 10 includes at least one base station (BS) 11. Respective BSs 11provide a communication service to particular geographical areas 15 a,15 b, and 15 c (which are generally called cells). Each cell may bedivided into a plurality of areas (which are called sectors). A userequipment (UE) 12 may be fixed or mobile and may be referred to by othernames such as mobile station (MS), mobile terminal (MT), user terminal(UT), subscriber station (SS), wireless device, personal digitalassistant (PDA), wireless modem, handheld device. The BS 11 generallyrefers to a fixed station that communicates with the UE 12 and may becalled by other names such as evolved-NodeB (eNB), base transceiversystem (BTS), access point (AP), etc.

In general, a UE belongs to one cell, and the cell to which a UE belongsis called a serving cell. A BS providing a communication service to theserving cell is called a serving BS. The wireless communication systemis a cellular system, so a different cell adjacent to the serving cellexists. The different cell adjacent to the serving cell is called aneighbor cell. A BS providing a communication service to the neighborcell is called a neighbor BS. The serving cell and the neighbor cell arerelatively determined based on a UE.

This technique can be used for downlink or uplink. In general, downlinkrefers to communication from the BS 11 to the UE 12, and uplink refersto communication from the UE 12 to the BS 11. In downlink, a transmittermay be part of the BS 11 and a receiver may be part of the UE 12. Inuplink, a transmitter may be part of the UE 12 and a receiver may bepart of the BS 11.

The wireless communication system may be any one of a multiple-inputmultiple-output (MIMO) system, a multiple-input single-output (MISO)system, a single-input single-output (SISO) system, and a single-inputmultiple-output (SIMO) system. The MIMO system uses a plurality oftransmission antennas and a plurality of reception antennas. The MISOsystem uses a plurality of transmission antennas and a single receptionantenna. The SISO system uses a single transmission antenna and a singlereception antenna. The SIMO system uses a single transmission antennaand a plurality of reception antennas. Hereinafter, a transmissionantenna refers to a physical or logical antenna used for transmitting asignal or a stream, and a reception antenna refers to a physical orlogical antenna used for receiving a signal or a stream.

FIG. 2 shows structure of a radio frame of 3GPP LTE. Referring to FIG.2, a radio frame includes 10 subframes. A subframe includes two slots intime domain. A time for transmitting one subframe is defined as atransmission time interval (TTI). For example, one subframe may have alength of 1 millisecond (ms), and one slot may have a length of 0.5 ms.One slot includes a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in time domain. Since the 3GPP LTE uses theOFDMA in the downlink, the OFDM symbol is for representing one symbolperiod. The OFDM symbols may be called by other names depending on amultiple-access scheme. For example, when SC-FDMA is in use as an uplinkmulti-access scheme, the OFDM symbols may be called SC-FDMA symbols. Aresource block (RB) is a resource allocation unit, and includes aplurality of contiguous subcarriers in one slot. The structure of theradio frame is shown for exemplary purposes only. Thus, the number ofsubframes included in the radio frame or the number of slots included inthe subframe or the number of OFDM symbols included in the slot may bemodified in various manners.

3GPP LTE defines that one slot includes seven 01-DM symbols in a normalcyclic prefix (CP) and one slot includes six OFDM symbols in an extendedCP.

The wireless communication system may be divided into a frequencydivision duplex (FDD) scheme and a time division duplex (TDD) scheme.According to the FDD scheme, an uplink transmission and a downlinktransmission are made at different frequency bands. According to the TDDscheme, an uplink transmission and a downlink transmission are madeduring different periods of time at the same frequency band. A channelresponse of the TDD scheme is substantially reciprocal. This means thata downlink channel response and an uplink channel response are almostthe same in a given frequency band. Thus, the TDD-based wirelesscommunication system is advantageous in that the downlink channelresponse can be obtained from the uplink channel response. In the TDDscheme, the entire frequency band is time-divided for uplink anddownlink transmissions, so a downlink transmission by the BS and anuplink transmission by the UE cannot be simultaneously performed. In aTDD system in which an uplink transmission and a downlink transmissionare discriminated in units of subframes, the uplink transmission and thedownlink transmission are performed in different subframes.

Frame structure type 1 is applicable to both full duplex and half duplexFDD. Each radio frame is T_(f)=307200×T_(s)=10 ms long and consists of20 slots of length T_(slot)=15360×T_(s)=0.5 ms, numbered from 0 to 19. Asubframe is defined as two consecutive slots where subframe i consistsof slots 2i and 2i+1.

For FDD, 10 subframes are available for downlink transmission and 10subframes are available for uplink transmissions in each 10 ms interval.Uplink and downlink transmissions are separated in the frequency domain.In half-duplex FDD operation, the UE cannot transmit and receive at thesame time while there are no such restrictions in full-duplex FDD.

Frame structure type 2 is applicable to TDD. Each radio frame of lengthT_(f)=307200×T_(s)=10 ms consists of two half-frames of length153600×T_(s)=5 ms each. Each half-frame consists of five subframes oflength 30720×T_(s)=1 ms. The supported uplink-downlink configurationsare listed in Table 1.

TABLE 1 Uplink- Downlink- downlink to-Uplink config- Switch-pointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 msD S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D DD D 6 5 ms D S U U U D S U U D

In Table 1, for each subframe in a radio frame, “D” denotes the subframeis reserved for downlink transmissions, “U” denotes the subframe isreserved for uplink transmissions and “S” denotes a special subframewith the three fields downlink pilot time slot (DwPTS), guard period(GP) and uplink pilot time slot (UpPTS). Each subframe i is defined astwo slots, 2i and 2i+1 of length T_(slot)=15360×T_(s)=0.5 ms in eachsubframe.

Uplink-downlink configurations with both 5 ms and 10 msdownlink-to-uplink switch-point periodicity are supported. In case of 5ms downlink-to-uplink switch-point periodicity, the special subframeexists in both half-frames. In case of 10 ms downlink-to-uplinkswitch-point periodicity, the special subframe exists in the firsthalf-frame only. Subframes 0 and 5 and DwPTS are always reserved fordownlink transmission. UpPTS and the subframe immediately following thespecial subframe are always reserved for uplink transmission.

In case multiple cells are aggregated, the UE may assume that the guardperiod of the special subframe in the different cells have an overlap ofat least 1456×T_(s). In case multiple cells with differentuplink-downlink configurations are aggregated and the UE is not capableof simultaneous reception and transmission in the aggregated cells, thefollowing constraints apply:

-   -   if the subframe in the primary cell is a downlink subframe, the        UE shall not transmit any signal or channel on a secondary cell        in the same subframe    -   if the subframe in the primary cell is an uplink subframe, the        UE is not expected to receive any downlink transmissions on a        secondary cell in the same subframe    -   if the subframe in the primary cell is a special subframe and        the same subframe in a secondary cell is a downlink subframe,        the UE is not expected to receive physical downlink shared        channel (PDSCH)/enhanced physical downlink control channel        (EPDCCH)/physical multicast channel (PMCH)/positioning reference        signal (PRS) transmissions in the secondary cell in the same        subframe, and the UE is not expected to receive any other        signals on the secondary cell in OFDM symbols that overlaps with        the guard period or UpPTS in the primary cell.

FIG. 3 shows a resource grid for one downlink slot. Referring to FIG. 3,a downlink slot includes a plurality of OFDM symbols in time domain. Itis described herein that one downlink slot includes 7 OFDM symbols, andone RB includes 12 subcarriers in frequency domain as an example.However, the present invention is not limited thereto. Each element onthe resource grid is referred to as a resource element (RE). One RBincludes 12×7 resource elements. The number N^(DL) of RBs included inthe downlink slot depends on a downlink transmit bandwidth. Thestructure of an uplink slot may be same as that of the downlink slot.

The number of OFDM symbols and the number of subcarriers may varydepending on the length of a CP, frequency spacing, and the like. Forexample, in case of a normal CP, the number of OFDM symbols is 7, and incase of an extended CP, the number of OFDM symbols is 6. One of 128,256, 512, 1024, 1536, and 2048 may be selectively used as the number ofsubcarriers in one OFDM symbol.

FIG. 4 shows structure of a downlink subframe. Referring to FIG. 4, amaximum of three OFDM symbols located in a front portion of a first slotwithin a subframe correspond to a control region to be assigned with acontrol channel. The remaining OFDM symbols correspond to a data regionto be assigned with a physical downlink shared chancel (PDSCH). Examplesof downlink control channels used in the 3GPP LTE includes a physicalcontrol format indicator channel (PCFICH), a physical downlink controlchannel (PDCCH), a physical hybrid automatic repeat request (HARQ)indicator channel (PHICH), etc. The PCFICH is transmitted at a firstOFDM symbol of a subframe and carries information regarding the numberof OFDM symbols used for transmission of control channels within thesubframe. The PHICH is a response of uplink transmission and carries anHARQ acknowledgment (ACK)/non-acknowledgment (NACK) signal. Controlinformation transmitted through the PDCCH is referred to as downlinkcontrol information (DCI). The DCI includes uplink or downlinkscheduling information or includes an uplink transmit (Tx) power controlcommand for arbitrary UE groups.

The PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, a resource allocation of anupper-layer control message such as a random access response transmittedon the PDSCH, a set of Tx power control commands on individual UEswithin an arbitrary UE group, a Tx power control command, activation ofa voice over IP (VoIP), etc. A plurality of PDCCHs can be transmittedwithin a control region. The UE can monitor the plurality of PDCCHs. ThePDCCH is transmitted on an aggregation of one or several consecutivecontrol channel elements (CCEs). The CCE is a logical allocation unitused to provide the PDCCH with a coding rate based on a state of a radiochannel. The CCE corresponds to a plurality of resource element groups.

A format of the PDCCH and the number of bits of the available PDCCH aredetermined according to a correlation between the number of CCEs and thecoding rate provided by the CCEs. The BS determines a PDCCH formataccording to a DCI to be transmitted to the UE, and attaches a cyclicredundancy check (CRC) to control information. The CRC is masked with aunique identifier (referred to as a radio network temporary identifier(RNTI)) according to an owner or usage of the PDCCH. If the PDCCH is fora specific UE, a unique identifier (e.g., cell-RNTI (C-RNTI)) of the UEmay be masked to the CRC. Alternatively, if the PDCCH is for a pagingmessage, a paging indicator identifier (e.g., paging-RNTI (P-RNTI)) maybe masked to the CRC. If the PDCCH is for system information (morespecifically, a system information block (SIB) to be described below), asystem information identifier and a system information RNTI (SI-RNTI)may be masked to the CRC. To indicate a random access response that is aresponse for transmission of a random access preamble of the UE, arandom access-RNTI (RA-RNTI) may be masked to the CRC.

FIG. 5 shows structure of an uplink subframe. Referring to FIG. 5, anuplink subframe can be divided in a frequency domain into a controlregion and a data region. The control region is allocated with aphysical uplink control channel (PUCCH) for carrying uplink controlinformation. The data region is allocated with a physical uplink sharedchannel (PUSCH) for carrying user data. When indicated by a higherlayer, the UE may support a simultaneous transmission of the PUSCH andthe PUCCH. The PUCCH for one UE is allocated to an RB pair in asubframe. RBs belonging to the RB pair occupy different subcarriers inrespective two slots. This is called that the RB pair allocated to thePUCCH is frequency-hopped in a slot boundary. This is said that the pairof RBs allocated to the PUCCH is frequency-hopped at the slot boundary.The UE can obtain a frequency diversity gain by transmitting uplinkcontrol information through different subcarriers according to time.

Uplink control information transmitted on the PUCCH may include a hybridautomatic repeat request (HARQ) acknowledgement/non-acknowledgement(ACK/NACK), a channel quality indicator (CQI) indicating the state of adownlink channel, a scheduling request (SR), and the like.

The PUSCH is mapped to an uplink shared channel (UL-SCH), a transportchannel Uplink data transmitted on the PUSCH may be a transport block, adata block for the UL-SCH transmitted during the TTI. The transportblock may be user information. Or, the uplink data may be multiplexeddata. The multiplexed data may be data obtained by multiplexing thetransport block for the UL-SCH and control information. For example,control information multiplexed to data may include a CQI, a precodingmatrix indicator (PMI), an HARQ, a rank indicator (RI), or the like. Orthe uplink data may include only control information.

Carrier aggregation (CA) is described. It may be referred to Section 5.5of 3GPP TS 36.300 V11.6.0 (2013-06).

In CA, two or more component carriers (CCs) are aggregated in order tosupport wider transmission bandwidths up to 100 MHz or more. A UE maysimultaneously receive or transmit on one or multiple CCs depending onits capabilities. A UE with single timing advance capability for CA cansimultaneously receive and/or transmit on multiple CCs corresponding tomultiple serving cells sharing the same timing advance (multiple servingcells grouped in one timing advance group (TAG)). A UE with multipletiming advance capability for CA can simultaneously receive and/ortransmit on multiple CCs corresponding to multiple serving cells withdifferent timing advances (multiple serving cells grouped in multipleTAGs). E-UTRAN ensures that each TAG contains at least one serving cell.A non-CA capable UE can receive on a single CC and transmit on a singleCC corresponding to one serving cell only (one serving cell in one TAG).

A serving cell is combination of downlink and optionally uplinkresources. That is, a serving cell may consist of one DL CC and one ULCC. Alternatively, a serving cell may consist of one DL CC. CA may havea plurality of serving cells. The plurality of serving cells may consistof one primary serving cell (PCell) and at least one secondary servingcell (SCell). PUCCH transmission, random access procedure, etc., may beperformed only in the PCell.

FIG. 6 shows an example of a carrier aggregation of 3GPP LTE-A.Referring to FIG. 6, each CC has a bandwidth of 20 MHz, which is abandwidth of 3GPP LTE. Up to 5 CCs or more may be aggregated, so maximumbandwidth of 100 MHz or more may be configured.

CA is supported for both contiguous and non-contiguous CCs with each CClimited to a maximum of 110 RBs in the frequency domain using theRel-8/9 numerology.

It is possible to configure a UE to aggregate a different number of CCsoriginating from the same eNB and of possibly different bandwidths inthe UL and the DL. The number of DL CCs that can be configured dependson the DL aggregation capability of the UE. The number of UL CCs thatcan be configured depends on the UL aggregation capability of the UE. Intypical TDD deployments, the number of CCs and the bandwidth of each CCin UL and DL is the same. A number of TAGs that can be configureddepends on the TAG capability of the UE.

CCs originating from the same eNB need not to provide the same coverage.

CCs shall be LTE Rel-8/9 compatible. Nevertheless, existing mechanisms(e.g., barring) may be used to avoid Rel-8/9 UEs to camp on a CC.

The spacing between center frequencies of contiguously aggregated CCsshall be a multiple of 300 kHz. This is in order to be compatible withthe 100 kHz frequency raster of Rel-8/9 and at the same time preserveorthogonality of the subcarriers with 15 kHz spacing. Depending on theaggregation scenario, the n×300 kHz spacing can be facilitated byinsertion of a low number of unused subcarriers between contiguous CCs.

For TDD CA, the downlink/uplink configuration is identical acrosscomponent carriers in the same band and may be the same or differentacross component carriers in different bands.

Dual connectivity is described.

FIG. 7 shows an example of dual connectivity to a macro cell and a smallcell. Referring to FIG. 5, the UE is connected to both the macro celland the small cell. A macro cell eNB serving the macro cell is the MeNBin dual connectivity, and a small cell eNB serving the small cell is theSeNB in dual connectivity. The MeNB is an eNB which terminates at leastS1-MME and therefore act as mobility anchor towards the CN in dualconnectivity. If a macro eNB exists, the macro eNB may function as theMeNB, generally. The SeNB is an eNB providing additional radio resourcesfor the UE, which is not the MeNB, in dual connectivity. The SeNB may begenerally configured for transmitting best effort (BE) type traffic,while the MeNB may be generally configured for transmitting other typesof traffic such as VoIP, streaming data, or signaling data. In the dualconnectivity, the UE may configured with one carrier group per each eNBin which all the carriers are configured with one PUCCH carrier whereall HARQ-ACK and feedback are transmitted from carriers configured byone eNB.

The interface between the MeNB and SeNB is called Xn interface. The Xninterface is assumed to be non-ideal, i.e., the delay in Xn interfacecould be up to 60 ms.

Uplink power control according to the current specification of 3GPP LTEis described. It may be referred to Section of 5.1 of 3GPP TS 36.213V11.3.0 (2013-06). For PUSCH, the transmit power {circumflex over(P)}_(PUSCH,C)(i) is first scaled by the ratio of the number of antennasports with a non zero PUSCH transmission to the number of configuredantenna ports for the transmission scheme. The resulting scaled power isthen split equally across the antenna ports on which the non-zero PUSCHis transmitted. For PUCCH or sounding reference signal (SRS), thetransmit power P _(PUCCH)(i) or {circumflex over (P)}_(SRS,C)(i) issplit equally across the configured antenna ports for PUCCH or SRS.{circumflex over (P)}_(SRS,C)(i) is the linear value of P_(SRS,c)(i).

Uplink power control for the PUSCH is described. The setting of the UEtransmission power for a PUSCH transmission may be defined as follows.If the UE transmits PUSCH without a simultaneous PUCCH for the servingcell c, then the UE transmit power P_(PUSCH,c)(i) for PUSCH transmissionin subframe i for the serving cell c may be given by Equation 1.

$\begin{matrix}{{P_{{PUSCH},c}(i)} = {\min {\begin{Bmatrix}{{P_{{CMAX},c}(i)},} \\{{10{\log_{10}( {M_{{PUSCH},c}(i)} )}} + {P_{{O\; \_ \; {PUSCH}},c}(j)} +} \\{{{\alpha_{c}(j)} \cdot {PL}_{c}} + {\Delta_{{TF},c}(i)} + {f_{c}(i)}}\end{Bmatrix}\lbrack{dBm}\rbrack}}} & {\text{<}{Equation}\mspace{14mu} 1\text{>}}\end{matrix}$

If the UE transmits PUSCH simultaneous with PUCCH for the serving cellc, then the UE transmit power P_(PUSCH,c)(i) for the PUSCH transmissionin subframe i for the serving cell c may be given by Equation 2.

$\begin{matrix}{{P_{{PUSCH}.c}(i)} = {\min {\begin{Bmatrix}{{10{\log_{10}( {{{\hat{P}}_{{CMAX},c}(i)} - {{\hat{P}}_{PUCCH}(i)}} )}},} \\{{10{\log_{10}( {M_{{PUSCH},c}(i)} )}} + {P_{{O\; \_ \; {PUSCH}},c}(j)} +} \\{{{\alpha_{c}(j)} \cdot {PL}_{c}} + {\Delta_{{TF},c}(i)} + {f_{c}(i)}}\end{Bmatrix}\lbrack{dBm}\rbrack}}} & {\text{<}{Equation}\mspace{14mu} 2\text{>}}\end{matrix}$

If the UE is not transmitting PUSCH for the serving cell c, for theaccumulation of transmit power control (TPC) command received with DCIformat 3/3A for PUSCH, the UE shall assume that the UE transmit powerP_(PUSCH,c)(i) for the PUSCH transmission in subframe i for the servingcell c may be computed by Equation 3.

P _(PUSCH,c)(i)=min{P _(CMAX,c)(i),P _(O) _(_) _(PUSCH,c)(1)+α_(c)(1)·PL_(c) +f _(c)(i)}[dBm]  <Equation 3>

In equations described above, P_(CMAX,c)(i) is the configured UEtransmit power in subframe i for serving cell c and {circumflex over(P)}_(CMAX,c)(i) is the linear value of P_(CMAX,c)(i). {circumflex over(P)}_(PUCCH)(i) is the linear value of P_(PUCCH)(i) described below.M_(PUSCH,c)(i) is the bandwidth of the PUSCH resource assignmentexpressed in number of resource blocks valid for subframe i and servingcell c. P_(O) _(_) _(PUSCH,c)(j) is a parameter composed of the sum of acomponent P_(O) _(_) _(NOMINAL) _(_) _(PUSCH,c)(j) provided from higherlayers for j=0 and 1 and a component P_(O) _(_) _(UE) _(_) _(PUSCH,c)(j)provided by higher layers for j=0 and 1 for serving cell c. PL_(c) isthe downlink pathloss estimate calculated in the UE for serving cell cin dB and PLc=referenceSignalPower—higher layer filtered referencesignal received power (RSRP), where referenceSignalPower is provided byhigher layers and RSRP and the higher layer filter configuration aredefined for the reference serving cell. If serving cell c belongs to atiming advance group (TAG) containing the primary cell then, for theuplink of the primary cell, the primary cell is used as the referenceserving cell for determining referenceSignalPower and higher layerfiltered RSRP. For the uplink of the secondary cell, the serving cellconfigured by the higher layer parameter pathlosSReferenceLinking isused as the reference serving cell for determining referenceSignalPowerand higher layer filtered RSRP. If serving cell c belongs to a TAG notcontaining the primary cell then serving cell c is used as the referenceserving cell for determining referenceSignalPower and higher layerfiltered RSRP.

If the total transmit power of the UE would exceed {circumflex over(P)}_(CMAX)(i), the UE may scale {circumflex over (P)}_(PUSCH,c)(i) forthe serving cell c in subframe i such that Equation 4 is satisfied.

$\begin{matrix}{{\sum\limits_{c}{{w(i)} \cdot {{\hat{P}}_{{PUSCH},c}(i)}}} \leq ( {{{\hat{P}}_{CMAX}(i)} - {{\hat{P}}_{PUCCH}(i)}} )} & {\text{<}{Equation}\mspace{14mu} 4\text{>}}\end{matrix}$

In Equation 4, {circumflex over (P)}_(PUSCH,C)(i) is the linear value ofP_(PUCCH)(i), {circumflex over (P)}_(PUSCH,C)(i) is the linear value ofP_(PUSCH,c)(i), {circumflex over (P)}_(CMAX)(i) is the linear value ofthe UE total configured maximum output power P_(CMAX) in subframe i andw(i) is a scaling factor of {circumflex over (P)}_(PUSCH,C)(i) forserving cell c where 0≦w(i)≦1. In case there is no PUCCH transmission insubframe i, {circumflex over (P)}_(PUCCH)(i)=0.

If the UE has PUSCH transmission with uplink control information (UCI)on serving cell j and PUSCH without UCI in any of the remaining servingcells, and the total transmit power of the UE would exceed {circumflexover (P)}_(CMAX)(i) the UE may scale {circumflex over (P)}_(PUSCH,C)(i)for the serving cells without UCI in subframe i such that Equation 5 issatisfied.

$\begin{matrix}{{\sum\limits_{c \neq j}{{w(i)} \cdot {{\hat{P}}_{{PUSCH},c}(i)}}} \leq ( {{{\hat{P}}_{CMAX}(i)} - {{\hat{P}}_{{PUSCH},j}(i)}} )} & {\text{<}{Equation}\mspace{14mu} 5\text{>}}\end{matrix}$

{circumflex over (P)}_(PUSCH,C)(i) is the PUSCH transmit power for thecell with UCI and w(i) is a scaling factor of {circumflex over(P)}_(PUSCH,C)(i) for serving cell c without UCI. In this case, no powerscaling is applied to P _(PUSCH,j)(i) unless

${\sum\limits_{c \neq j}{{w(i)} \cdot {{\hat{P}}_{{PUSCH},c}(i)}}} = 0$

and the total transmit power of the UE still would exceed {circumflexover (P)}_(CMAX)(i) Note that w(i) values are the same across servingcells when w(i)>0 but for certain serving cells w(i) may be zero.

If the UE has simultaneous PUCCH and PUSCH transmission with UCI onserving cell j and PUSCH transmission without UCI in any of theremaining serving cells, and the total transmit power of the UE wouldexceed {circumflex over (P)}_(CMAX)(i), the UE may obtain {circumflexover (P)}_(PUSCH,C)(i) according to Equation 6.

$\begin{matrix}{{{{\hat{P}}_{{PUSCH},j}(i)} = {\min ( {{{\hat{P}}_{{PUSCH},j}(i)},( {{{\hat{P}}_{CMAX}(i)} - {{\hat{P}}_{PUCCH}(i)}} )} )}}{{\sum\limits_{c \neq j}{{w(i)} \cdot {{\hat{P}}_{{PUSCH},c}(i)}}} \leq ( {{{\hat{P}}_{CMAX}(i)} - {{\hat{P}}_{PUCCH}(i)} - {{\hat{P}}_{{PUSCH},j}(i)}} )}} & {\text{<}{Equation}\mspace{14mu} 6\text{>}}\end{matrix}$

If the UE is configured with multiple TAGs, and if the PUCCH/PUSCHtransmission of the UE on subframe i for a given serving cell in a TAGoverlaps some portion of the first symbol of the PUSCH transmission onsubframe i+1 for a different serving cell in another TAG, the UE shalladjust its total transmission power to not exceed P_(CMAX) on anyoverlapped portion.

If the UE is configured with multiple TAGs, and if the PUSCHtransmission of the UE on subframe i for a given serving cell in a TAGoverlaps some portion of the first symbol of the PUCCH transmission onsubframe i+1 for a different serving cell in another TAG, the UE shalladjust its total transmission power to not exceed P_(CMAX) on anyoverlapped portion.

If the UE is configured with multiple TAGs, and if the SRS transmissionof the UE in a symbol on subframe i for a given serving cell in a TAGoverlaps with the PUCCH/PUSCH transmission on subframe I or subframe i+1for a different serving cell in the same or another TAG, the UE shalldrop SRS if its total transmission power exceeds P_(CMAX) on anyoverlapped portion of the symbol.

If the UE is configured with multiple TAGs and more than 2 servingcells, and if the SRS transmission of the UE in a symbol on subframe ifor a given serving cell overlaps with the SRS transmission on subframei for a different serving cell(s) and with PUSCH/PUCCH transmission onsubframe i or subframe i+1 for another serving cell(s), the UE shalldrop the SRS transmissions if the total transmission power exceedsP_(CMAX) on any overlapped portion of the symbol.

If the UE is configured with multiple TAGs, the UE shall, when requestedby higher layers, to transmit physical random access channel (PRACH) ina secondary serving cell in parallel with SRS transmission in a symbolon a subframe of a different serving cell belonging to a different TAG,drop SRS if the total transmission power exceeds P_(CMAX) on anyoverlapped portion in the symbol.

If the UE is configured with multiple TAGs, the UE shall, when requestedby higher layers, to transmit PRACH in a secondary serving cell inparallel with PUSCH/PUCCH in a different serving cell belonging to adifferent TAG, adjust the transmission power of PUSCH/PUCCH so that itstotal transmission power does not exceed P_(CMAX) on the overlappedportion.

Uplink power control for the PUCCH is described. If serving cell c isthe primary cell, the setting of the UE transmission power P_(PUCCH) forthe PUCCH transmission in subframe i may be defined by Equation 7.

$\begin{matrix}{{P_{PUCCH}(i)} = {\min {\begin{Bmatrix}{{P_{{CMAX},c}(i)},} \\{P_{0\_ \; {PUCCH}} + {PL}_{c} + {h( {n_{CQI},n_{HARQ},n_{SR}} )} +} \\{{\Delta_{F\; \_ \; {PUCCH}}(F)} + {\Delta_{TxD}( F^{\prime} )} + {g(i)}}\end{Bmatrix}\lbrack{dBm}\rbrack}}} & {\text{<}{Equation}\mspace{14mu} 7\text{>}}\end{matrix}$

If the UE is not transmitting PUCCH for the primary cell, for theaccumulation of TPC command received with DCI format 3/3A for PUCCH, theUE shall assume that the UE transmit power P_(PUCCH) for the PUCCHtransmission in subframe i may be computed by Equation 8.

P _(PUCCH)(i)=min{P _(CMAX,c)(i),P _(O) _(_) _(PUCCH) +PL _(c)+g(i)}[dBm]  <Equation 8>

In equations described above, P_(CMAX,c)(i) is the configured UEtransmit power in subframe i for serving cell c. The parameter Δ_(F)_(_) _(PUCCH)(F) is provided by higher layers. If the UE is configuredby higher layers to transmit PUCCH on two antenna ports, the value ofΔ_(T×D)(F′) is provided by higher layers. Otherwise, Δ_(T×D)(F′)=0.h(n_(CQI), H_(HARQ), n_(SR)) is a PUCCH format dependent value, wheren_(CQI) corresponds to the number of information bits for the channelquality information (CQI). n_(SR)=1 if subframe i is configured for SRfor the UE not having any associated transport block for UL-SCH,otherwise n_(SR)=0=0. P_(O) _(_) _(PUCCH) is a parameter composed of thesum of a parameter P_(O) _(_) _(NOMINAL) _(_) _(PUCCH) provided byhigher layers and a parameter P_(O) _(_) _(UE) _(_) _(PUCCH) provided byhigher layers.

Hereinafter, a method for controlling uplink power according toembodiments of the present invention is described. An embodiment of thepresent invention may propose power control aspects when inter-sitecarrier aggregation is used for a UE. Inter-site carrier aggregation maybe defined as that a UE is configured with multiple carriers where atleast two carriers are associated with separate eNBs which may beconnected by ideal backhaul or non-ideal backhaul.

Meanwhile, when a UE is configured with dual connectivity, there couldbe a case that MeNB and SeNB are not synchronized each other and theymay not be aware of timing of each other. In that case, it is natural toallow separate configuration and separate trigger of power headroomreport (PHR) and power control.

For the uplink, the power availability, or power headroom may be definedas the difference between the maximum output power and the estimatedoutput power for UL-SCH. The power headroom may be positive as well asnegative (on a dB scale), where a negative value may indicate that thenetwork has scheduled a higher data rate than the UE can support withcurrent power availability. The power headroom may depend on thepower-control mechanism and be influenced by the interference in thesystem and the distance to the base stations, etc. To assist theselection of a combination of modulation-and-coding scheme (MCS) andresource size M that does not lead to the UE whose power is limited, theUE may be configured to provide regular PHRs on usage of the UE's powerusage. There may be a separate transmit-power limitation for eachcomponent carrier. Thus, power headroom may be measured and reportedseparately for each component carrier.

Information about the power headroom (i.e. PHR) is fed back from the UEto the eNB. Type-1 PHR is provided for all component carriers (CCs)simultaneously, while Type-2 PHR is provided for the primary componentcarrier only.

Handling Asynchronous MeNB and SeNB Case

When PHR utilizes all the activated uplink-configured carriers for bothMeNB and SeNB, this asynchronous situation may cause some confusion.

Let's assume that a PHR is triggered for MeNB at subframe n in MeNBconfiguration, subframe n+k or n+k+1 in SeNB configuration. Due to thefact that frame boundary may not be aligned between MeNB and SeNB, itwould be possible that subframe index n+k and n+k+1 both have overlapwith subframe n of MeNB.

In this case, when a UE calculated PHR values for carriers configuredfor SeNB needs to make a decision on which subframe would be used forPHR computation (either n+k or n+k+1). Since each subframe may havedifferent uplink transmissions such as PUCCH, PUSCH or PUCCH/PUSCH, thereported PHR would be different as well.

In terms of reporting, it would be desirable to report the worst case.Thus, among two subframes, UE can report less power headroom value wheretype1 and type2 are reported for S-PCell. The similar principle can beapplied to SeNB PHR reporting as well. Alternatively, a UE can selecteither one and report it. Or, depending on the overlap portion, subframecan be selected. Or, always, first subframe (n+k) can be selected.Another alternative, of course, can be to send better PHR. In summary,UE may report min power headroom values of two, or max power headroomvalue of two.

Another approach to handle SeNB maximum power is to allocate two maximumpower values for SeNB. One is maximum power usable per carrier and theother one is maximum desired total power used for SeNB.

Assuming in terms of power, always SeNB will be deprioritized over MeNB,when reporting PHR, carriers configured for SeNB may use min {maximumpower per carrier, maximum desired total power for SeNB} as a maximumusable power per carrier such that MeNB can obtain the information howmuch power headroom for SeNB is present assuming a configured maximumpower for SeNB usable. Reversely, this can be applied to MeNB as well.

This approach would be useful when an eNB does not know the maximumallocated power to the other eNB for some reasons. For example, due tomaximum transmit power P_(CMAX) computation at UE (where powerallocation may be given by ratio—power sharing ratio between carriergroups) or due to UE computation on maximum power for each carriergroup, if maximum power per carrier group is not known to the network,instead of reporting maximum transmit power per-carrier P_(CMAX,c),maximum power per carrier group can be also used. When reporting maximumpower per carrier group, this value can be reported separately (or inaddition to) from P_(CMAX,c) where P_(CMAX,c) will be reported followingPHR reporting mechanism.

In terms of computing P_(CMAX), we think that overlapped subframes needsto be considered. FIG. 8 briefly describes an example of obtainingmaximum power considering the overlapped subframes according to thepresent invention(s). Subframes of MeNB and SeNB are not aligned becauseof asynchronization. Referring to FIG. 8, the n-th subframe for SeNB isoverlapped with k-th and (k+1)-th subframe for MeNB. To get the maximumpower at n-th subframe for SeNB, both maximum power from (n, k) andmaximum power from (n, k+1) need be considered.

To determine power limited case, P_(CMAX)(n,k) and P_(CMAX)(n, k+1) canbe used where power limited case can be examined in two overlap period(overlap between subframe n and k and between subframe n and k+1) usingP_(CMAX)(n,k) and P_(CMAX)(n, k+1) respectively. At least one overlaphas power limited case, it is considered as the power limited case.

At the overlap portion where power limited case occurs, power scalingrule may be applied. The computed power for a uplink channel can becalled as P_(ul)(n, k) and P_(ul)(n, k+1) for n-th subframetransmission. The power can be determined as min {P_(ul)(n,k), P_(ul)(n,k+1)}.

FIG. 9 briefly describes an example of power scaling according to thepresent invention(s). In the example of FIG. 9, subframes of carrier C1and carrier C2 are not aligned because of asynchronization. The powerfor carrier 2 (C2) at n-th subframe is determined as min {P2, P3} whereP2 and P3 are determined from each overlap portion following priorityrule.

That is, power for C2 for overlapped portion between n-th subframe ofcarrier C2 and k-th subframe of carrier C1 can be obtained as describedin second figure of FIG. 9 and power for C2 for overlapped portionbetween n-th subframe of C2 and (k+1)-th subframe of C1 can be obtainedas described in third figure of FIG. 9 when subframe of C2 and subframesof C1 are overlapped as first figure in FIG. 9. Consequently, power forC2 at n-th subframe can be determined as fourth figure in FIG. 9.

Uplink Transmission Delay

To handle power scaling on PUSCH transmission, an eNB may send “ULdelay” along with UL grant such that if UL delay is triggered, a UE hasflexibility to transmit PUSCH at subframe n+4 or n+5 depending on theavailable power. If transmission at (n+4)-th subframe has not cause anypower issue, it will transmit PUSCH at (n+4)-subframe. Otherwise, it canselect the better one between two subframes.

This would be useful when FDD/TDD are inter-node aggregated where FDDcan wait one subframe where TDD may change its direction from UL to DL.It can be also considered (generally speaking), UL delay would be morethan 1 subframe.

Handling Different Synchronous States for Power Control

In dual connectivity, depending on MeNB/SeNB configuration, a UE mayexperience two different cases where a UE may assume that two eNBs aresynchronized so that the uplink transmission to both eNBs can occursimultaneously in the first case and a UE may experience large timingdifference between two eNBs and thus uplink transmission may need to beattempted separately (from implementation perspective).

As, to support the second case (asynchronous case) the UE complexityincreases, it is desirable to consider “enable” the support onasynchronous case only if needed by higher layer signaling.

Furthermore, it is also considerable to have different UE capability on“TPC support on asynchronous dual connectivity” where a UE may notsupport power control on asynchronous case due to its hardwarecomplexity. This capability may also specify whether the UE supportsasynchronous scenario or not in general.

In summary, a UE may report “TPC support on asynchronous scenario (ordual connectivity)” to higher layer as a capability, and a network mayconfigure a UE to use “TPC asynchronous case” when dual connectivity isconfigured. If a UE is not configured with “enableTPCasync” (TPCasynchronous case), it may assume that MeNB and SeNB are synchronized.Or, a separate higher layer signaling to indicate the synchronous statebetween two eNBs can be feasible as well.

It is also feasible that even if a UE supports asynchronous case (inthis case UE capability for reporting may be done), a UE may not want tobe configured with asynchronous dual connectivity scenario depending onother configurations. For example, asynchronous dual connectivity maynot be configured with ePDCCH. In this case, a UE may reject ePDCCHconfiguration or asynchronous dual connectivity configuration.

For synchronous scenario, the timing difference between MeNB and SeNBmay be assumed to be less than a threshold.

Alternatively, a UE can assume synchronous case based on transmissiontiming difference of signals to PCell and pSCell. For example, if thedifference is less than [33 μs], it can assume that the scenario is asynchronous case. Otherwise, it can assume that the network isasynchronized.

From the power control perspective, synchronized case means a UE appliespower control mode for synchronized scenario (for example, all theremaining power is shared between two eNBs and the priority rule basedon uplink control information (UCI) type is applied) whereas forasynchronous scenario is to utilize the priority rule based on earliertiming and the minimum reserved power is allocated towards the other eNBif there is potentially uplink transmission in the next overlappedsubframe.

Alternatively, received timing different between PCell and pSCell andtransmission timing difference to PCell and pSCell can be used todetermine whether the UE applies synchronous scenario or asynchronousscenario. For example, if the received timing difference is less than 33μs and transmission timing difference is less than [33 μs], the UE needsto assume it can perform look-ahead and thus applies priority rule basedon UCI type (which is applied in synchronous scenario) on the overlappedsubframes (larger overlapped one). Otherwise, it can assume asynchronouscase and then applies priority rule based on transmission timing(earlier transmission gets higher priority).

When a UE determines the synchronized scenario or asynchronized scenario(or power control mode to apply) based on transmission timing differenceof signals to PCell and pSCell (or signals to any cell), some conditionswhere transmission timing difference may change may suddenly need to beconsidered.

One example is to adjust timing advance (TA) based on RACH procedure(and thus absolute TA value is configured). Based on TA adjustment byRACH procedure, if the transmission timing difference becomes larger(>[33 μs]) from small value (such as [33 μs]), the UE may switch itspower control mode.

Note that when a UE determines power control based on uplinktransmission timing difference, it needs to be based on PUSCH or PUCCHtransmission timing rather than utilizing PRACH or SRS.

Alternatively, even with TA adjustment based RACH, a UE may performuplink timing difference based on a rather long-term scale measurementsand thus, if the average transmission timing difference is still lessthan a threshold [33 μs], it may still consider a synchronized mode(e.g., DC power control mode used in synchronized scenario). If theaverage changes, it may changes its behavior.

Another approach is to determine the transmission timing differencebetween PCell and pSCell based on current N_(TA) values or the instanttransmission timing difference between PCell and pSCell. If the powercontrol mode changes dynamically, the UE may apply the chosen powercontrol mode in the current subframe and may change its behavior for thenext subframe. For example, if subframe n of master carrier group (MCG)and subframe k and k+1 of secondary carrier group (SCG) overlap, the newDC power control may be applied starting subframe n+1 and k+2 (or k+1).

Another approach is to allow UE implementation solution to handle theswitch such that when a UE is configured with SeNB or pSCell, if thetransmission timing difference is less than [33 μs], the power controlis determined as synchronous (otherwise, it's determined asasynchronous). Once it is determined, unless pSCell changes ordeactivated, the same mode is applied. This may imply that a UE may haveto support synchronous power control mode (i.e., look-ahead operation)even though the transmission timing difference becomes larger than [33μs] at some point. A UE may trigger “error” if it cannot handle thesynchronous mode (or asynchronous mode) or stop transmitting to pSCellor drop the packet to pSCell only if the power limited case occurs.

In other words, a UE may have a choice to drop packets to pSCell (orSCG) if it is determined as synchronous power control mode where thetransmission timing difference becomes larger than [33 μs] and the powerlimited case occurs. That is, a UE can drop uplink channel(s) if itcannot apply the currently determined DC power control mode and the UEexperiences power limited case.

This is particularly true if the network signals which power controlmode is used. There may be two approach depending on whether the networksignaling is applied.

(1) Approach 1—the network signaling approach is used.

If the network signals DC power control mode 1, a UE shall apply DCpower control mode 1 as long as the transmission timing difference ofsignals to PCell and pSCell is equal to or less than [33 μs]. One of thefollowing for UE behavior if the transmission timing difference ofsignals to PCell and pSCell is larger than [33 μs]. (i) Alt1: Same asMTA, treat this case as an error case (i.e., not transmitting uplinksignals to SCG for example). (ii) Alt2: A UE may apply DC power controlmode 2 in this case.

If the network signals DC power control mode 2, a UE shall apply DCpower control mode 2 as long as the transmission timing difference ofsignals to PCell and pSCell is larger than [33 μs]. One of the followingon UE behavior if the transmission timing difference of signals to PCelland pSCell is equal to or less than [33 μs]. (i) Alt1: A UE shall applyDC power control mode 2 in this case. (ii) Alt2: A UE may not apply DCpower control mode 2 in this case.

(2) Approach 2

If the network signals DC power control mode 1, a UE can assume that thetransmission timing difference of signals to PCell and pSCell is equalto or less than [33 μs]. UE behavior may be one of the followings if thetransmission timing difference of signals to PCell and pSCell is largerthan [33 μs]. (i) Alt1: Same as CA, a UE may not transmit uplink signalto SCG (ii) Alt2: A UE informs the network and UE may not transmituplink signal to SCG

If the network signals DC power control mode 2, a UE can assume that thetransmission timing difference of signals to PCell and pSCell is largerthan [33 μs]. UE behavior if the transmission timing difference ofsignals to PCell and pSCell is equal to or less than [33 μs] may be oneof the followings. (i) Alt1: A UE shall apply DC power control mode 2 inthis case. (ii) Alt2: A UE apply DC power control mode 2 if processingtime allows allows or timing difference is less than [33 μs], otherwise,UE may not transmit uplink signals to SCG (iii) Alt3: A UE apply DCpower control mode 2 if processing time allows allows or timingdifference is less than [33 μs], otherwise, UE apply DC power controlmode 1. (iv) Alt4: UE apply DC power control mode 2 if processing timeallows or timing difference is less than [33 μs], otherwise, UE apply DCpower control mode 1 and inform the network it applies DC power controlmode 1. (v) Alt5: Leave to UE implementation to handle this case todetermine which DC power control mode is selected. (vi) Alt6: Leave toUE implementation to handle this case, and inform the network about DCpower control mode. (vii) Alt7: Leave to UE implementation includingwhether to drop UL to SCG or select power control.

It is up to UE implementation how to measure the transmission timingdifference. When it exceeds a certain threshold such as [33 μs], it canapply asynchronous power control mode. Otherwise, it can apply syncpower control mode. During the activated pSCell, the power control modemay not be changed. If it needs to be changed, it can be based on UEmeasurement and its up to UE implementation how to change.Alternatively, when the power limited case occurs, the UE measures thetiming difference and apply either power control mode based on thetransmission timing difference. Unless otherwise configured, UE shouldassume synchronous power control mode in case power limited case wouldnot occur (or assume synchronous power control mode to determine powerlimited case).

Alternatively, a UE may change its power control mode only when TA isreceived (either from MCG or SCG). Even though the transmission timingdifference may become larger than [33 μs] in between of TA commands, UEneed not to change the power control mode. Since it applies after 6 msecfrom TA commands, the same subframe would be the starting subframe toapply different power control mode if the mode is changed. In otherwords, the same rule for applying TA needs to be used for determiningdetermine power control mode. The timing difference is measured thusonly when TA command is received.

However, it does not imply that SFN between two eNBs are aligned orframe boundary is aligned. Rather, as long as subframe boundary isaligned between MeNB and SeNB, it can be assumed as a synchronousscenario.

In case, SFN and/or frame boundary is not aligned, a UE can beconfigured with offset in terms of subframe offset and/or SFN offset.Alternatively, a UE may report the offset to its serving cell as well.Based on the offset, when power control is performed, the overlappedsubframe is determined.

For example, if frame boundary of MeNB and SeNB has “3 subframe” offset,n-th subframe for MeNB and n+3-th subframe for SeNB are assumed as theoverlapped subframe.

Also, defining synchronous case also depend on the TA value differenceconfigured by MeNB and SeNB. Thus, the maximum difference of any TA fromMeNB and any TA from SeNB should not exceed a certain threshold that aUE can handle by multiple TA mechanism. Thus, the maximum allowable TAvalue for each eNB may be coordinated between two eNBs.

For example, the maximum TA value for SeNB may be assumed as zero ‘0’whereas the maximum TA value for MeNB may be assumed as maximum TAdifference in multiple TAG (such as 32.46 μs). When TA value exceeds theassigned maximum TA, either Radio Resource Control (RRC) reconfigurationis attempted to change the operation mode from synchronous TPC toasynchronous TPC or only the maximum TA is used or SeNB removal may beattempted.

More specifically, a UE supports only synchronized scenarios may informthe network TA difference becomes larger than its tolerable value suchthat the network may deconfigure SeNB. From the operation perspective,if uplink transmission difference between any TAG regardless of TAGbelonging to MCG or SCG is larger than the tolerable value, this casecan be treated as a mis-configuration or wrong scenario.

It is however notable that the difference between TA values from eacheNB needs to be maintained as lower than the threshold. Thus, actualvalue can exceed the threshold. When a UE operates in synchronous TPCmode, upon receiving TA gap larger than the threshold, it shall informMeNB.

For better handling of uplink power control and transmission, theconfiguration of asynchronous case or synchronous case is determined atSeNB addition. When SeNB is added to a UE, synchronization informationis given.

When a UE is configured with asynchronous dual connectivity (i.e., MeNBand SeNB are not synchronized), the UE may have to acquire PBCH toobtain SFN information of SeNB. As some information such as dedicatedPRACH resource or measurement may also depend on the knowledge on SFNinformation, when a UE reports measurement reports, it may also reportthe SFN and/or timing offset to MeNB of the identified cell (if it isdifferent from the MeNB). In case that a UE is not able to read PBCH,dedicated signaling such as via random access response to indicatesingle frequency network (SFN) can be considered.

Another indication of synchronous mode and asynchronous mode can beinferred from the sum of P_MeNB (allocated power for MeNB) and P_SeNB(allocated power for SeNB). If the sum exceeds the UE total power, theUE may assume that it operates in synchronous mode whereas in othercases, the UE can assume asynchronous mode.

In terms of TPC operation in synchronous case and asynchronous case, thefollowing (A) to (C) are different.

(A) P_(Cmax) determination: FIG. 10 describes an example of determiningP_(CMAX) in asynchronous case. Referring to FIG. 10, in asynchronouscase, P_(CMAX) is determined by following a new rule such asmin{P_(CMAX)1=CC1(n)+CC2(n), P_(CMAX)2=CC1(n)+CC2(n+1),P_(CMAX)3=CC1(n+1)+CC2(n+1)}, whereas in synchronous case, P_(CMAX) isdetermined per subframe n as in CA. Accordingly, power limited casedefinition is also affected.

(B) Power scaling: In terms of power sharing/scaling, in asynchronouscase, two overlapped subframe (n, n+1) needs to be accounted for thetransmission. Whereas synchronous case can utilize only subframe n.

(C) Power scaling rule/priority: In terms of priority rule, it can bethe same except that in synchronous case, a UE may reduce the powerduring the transmission of a channel following multiple TA handlingspecification.

To be more generic, power control in synchronous case can be called as“mode 1 power control operation” whereas power control in asynchronouscase can be called as “mode 2 power control operation”. When a UE isconfigured with different TAG per CG, if the TA difference betweendifferent TAG exceeds the maximum tolerable TA difference (such as 32.67μs) even though a UE is configured with mode 1 operation, it shallinform the network about the misconfiguration. Or, a UE may set the TAof SeNB=TA1 (MeNB)—maximum tolerable TA difference such that it canhandle different TAGs within a tolerance.

Power Control Optimization in Synchronous Mode Operation:

Extending Rel-11 of LTE CA power control for synchronous mode needs somefurther considerations.

FIG. 11 briefly illustrates a case that PUCCH at (n+1)-th subframe onMeNB and PUCCH at n-th subframe on SeNB are overlapped. Assuming thatPUCCH has higher priority than PUSCH and MeNB has higher priority overSeNB when PUCCH and PUCCH collide in the power-limited case.

Referring to FIG. 11, since SeNB PUCCH has higher priority over PUSCH onMeNB, SeNB PUCCH can be transmitted without power scaling at n-thsubframe. However, since PUCCH at n-th subframe overlaps with PUCCH onMeNB at n+1 th subframe, the power scaling in the overlapped portion isneeded.

According to current existing rule (such as 3GPP LTE rel-11), a UE mayadjust power not to exceed P_(CMAX) in the overlapped portion whichleads scaling on PUCCH in that overlapped region. To avoid the powerscaling in the overlapped portion, some other mechanisms such as {circlearound (1)}˜{circle around (4)} can be considered.

{circle around (1)} To determine the power of PUCCH, it shall look atboth n and n+1 subframe of the other eNB (or only PUCCH on SeNB may lookat n and n+1 subframe of MeNB). If there is power limited case occurs byPUCCH/PUCCH collision, according to the priority rule, PUCCH to SeNB canbe dropped. In the example, PUCCH on n-th subframe can be dropped.{circle around (2)} A UE can be higher layer configured with usingshortened PUCCH for SeNB (assuming PUCCH on MeNB has higher priority, ifSeNB PUCCH has higher priority, shortened PUCCH on MeNB can beconfigured). Since shortened PUCCH format for PUCCH format2 is notavailable, when PUCCH format 2 is transmitted in a power limited case,power scaling may be used if PUCCH is not dropped. If shortened PUCCH isconfigured for this matter, a UE shall use shortened PUCCH regardless ofSRS transmission or SRS configuration.{circle around (3)} Power scale the whole PUCCH not to exceed UE maximumpower within 1 msec (i.e., during PUCCH transmission). Since the overlapportion is very small (such as 32.46 μs), if the exceeded power isscaled over the entire PUCCH transmission duration, the reduced powercan be very marginal and thus the performance of impact on PUCCH may notbe significant.{circle around (4)} Another way is to drop the latter PUCCH in the powerlimited case. Assuming a UE only monitors subframe n for uplinktransmission for n-th subframe, if PUCCH at n-th subframe with PUCCH atn+1 th subframe collide, n+1th subframe PUCCH can be dropped if the UEexperiences power limited case. Or, power scale the whole PUCCH on n+1th subframe PUCCH (per method {circle around (3)}) can be attemptedwhere the exceeded power can be spread over the entire PUCCHtransmission of n+1th subframe PUCCH. In this case, it can be generallysaid that transmission power of prior uplink transmission would not bechanged due to the successive uplink transmissions in any condition.

For other collision cases, PUSCH/PUCCH or PUCCH/PUSCH, a UE can reducethe power in the overlapped portion not to exceed UE maximum power.

Note that a network may configure to apply multiple TA behavior in thiscase as well. Or, a UE may assume to apply the same behavior if theoverlap portion (smaller overlap) is small. Moreover, even withconfigured with carrier groups, if it is within an eNB (i.e., intra-eNBCA), MTA behavior shall be followed. In other words, if a UE isconfigured with two carrier groups in a CA framework, if it is indicatedto a UE via higher layer signaling or by other means, it shall followMTA for that cases.

FIG. 12 briefly shows another example of a case that PUCCH and PRACHcollide.

If TA value for MeNB is greater than SeNB, the overlap may not occur.However, as shown in FIG. 12, MeNB PUCCH and SeNB PRACH may collidedepending on transmission timing of MeNB/SeNB and TA value settings(Similar thing can happen for MeNB PRACH as well). In this case, ifPRACH has higher priority over PUCCH, MeNB PUCCH may have to beadjusted.

The similar mechanism mentioned in above can be applied in this case aswell. However, since PRACH has relatively long preamble, reducing PRACHpower in the overlapped portion can be also considered. In other words,a UE may reduce power (with keeping PUCCH power) in the overlappedportion. Proper TA setting may avoid this issue as well. In this case, aUE can assume that PRACH at (n+1)-th subframe may not collide with anyuplink transmission in n-th subframe for the other eNB. If that occurs,UE may exceed the maximum power in the overlapped portion. Thus, anyother treatment is not necessary.

Asynchronous Case Handling when UE Cannot Perform Look-Ahead

It is agreed that the first transmission can utilize the remaining powerafter total power allocated per CG P_(alloc) _(_) _(xeNB) is reservedfor each xCG Even in this case, PRACH and SRS need to be able to performlook-ahead and thus, this discloser focuses on the PUCCH/PUSCH casesonly.

When a UE knows that there will be no uplink transmissions in subframe kand k+1 (when subframe n of one eNB and subframe k and k+1 of the othereNB overlap) in the other eNB, it is able to utilize the whole remainingpower.

Furthermore, considering protecting more power, it can be considered toconfigure a set of subframes where different P_(alloc) _(_) _(xeNB) canbe considered. For example, in enhanced interference management andtraffic adaptation (eIMTA), subframe #2 is very important to carry PUCCHwhereas other subframes may be able to use low power. For subframe #2,high allocated power can be considered whereas other subframes are usedwith lower allocated power not to limit power to MCG unnecessarily.

Moreover, SPS PUSCH can take higher priority over first transmission asit can be considered as “scheduled” transmission. Thus, the UE canreserve some power to SPS PUSCH (i.e., give higher priority over firsttransmission).

For example, if n+2 subframe transmits SPS PUSCH, k+2 and k+3 of theother eNB may use power up to P_(CMAX)−max{P_(alloc) _(_) _(MeNB), SPSPUSCH power}.

Alternatively, SCG transmission may utilize the remaining power onlywhen the UE assures that there will be no uplink transmissions to MCG inthe overlapped subframes.

Determining Power Limited when UE Cannot Perform Look-Ahead

FIG. 13 briefly shows an example of an asynchronous case between MeNBand SeNB. In the example of FIG. 13, n-th subframe of SeNB is overlappedwith k-th and (k+1)-th subframes of MeNB.

Referring to FIG. 13, to determine P_(CMAX) (and determine whether theUE is power limited or not) at subframe n for SeNB, a UE needs to lookat P_(CMAX,c) of MeNB at subframe k and k+1. Otherwise, it may exceed UEPpowerclass in any overlapped portion unless a UE may reduce the poweror increase the power in the middle of subframe of n.

In case, a UE does not know the power of subframe k+1, the UE may assumethe worst case power which is computed based on the worst caseassumption. Let's make an example that P_(CMAX,MeNB)(k)=P_(k). Then, thepower may be computed by equation 9.

$\begin{matrix}{{P_{{PUSCH},c}(i)} = {\min \begin{Bmatrix}{{{\hat{P}}_{{CMAX},c}(i)},} \\{{10{\log_{10}( {M_{{PUSCH},c}(i)} )}} + {P_{{O\; \_ \; {PUSCH}},c}(j)} +} \\{{{\alpha_{c}(j)} \cdot {PL}_{c}} + {\Delta_{{TF},c}(i)} + {f_{c}(i)}}\end{Bmatrix}}} & {\text{<}{Equation}\mspace{14mu} 9\text{>}}\end{matrix}$

If the UE knows that subframe k+1 is downlink subframe, then it isaccounted for the case the UE knows the power of k+1. If the UE knowsthat subframe k+1 is for PRACH, or corresponding to uplink transmissionwhich is scheduled at least 4 msec before (for example, as with TDDconfiguration such as TDD configuration 0), or it has SPS PUSCH whosescheduling information is known to UE, the cases are not considered aslook-ahead infeasible.

Look-ahead infeasible case is limited to the case where the UE does notknow the power of the latter subframe between two overlapped subframesfor some reasons. By any means such as by (semi)-static configurationsuch as DL/UL configuration, by SPS scheduling or by PRACH or by timing(the corresponding uplink grant such as PDCCH order or MAC layerindication) comes before the scheduling grant for subframe n or at leastbefore 2.5 msec before the current subframe n, a UE may assume that itknows the power of subframe k+1.

More generally, a UE may be assumed not to be able to look-aheadsubframe (k+1) if equation 10 is satisfied for starting time of (k+1)-thsubframe T1 and starting time of n-th subframe T2.

T1−T2>δ  <Equation 10>

Here, δ is a threshold which can be 0.5 msec or 100 μs.

Or, timing difference between two uplink carriers can be used todetermine whether the UE can perform look-ahead or not.

Alternatively, received timing different between PCell and pSCell andtransmission timing difference to PCell and pSCell can be used todetermine whether the UE applies synchronous scenario or asynchronousscenario. For example, if the received timing difference is less than 33μs and transmission timing difference is less than [33 μs], the UE mayassume that the UE can perform look-ahead and thus applies priority rulebased on UCI type on the overlapped subframes (larger overlapped one).Otherwise, the UE may assume it is an asynchronous case.

Also, whether a UE is scheduled with EPDCCH or not can be a factor aswell. It can be up to the UE. However, when the information is notavailable, P_(CMAX) can be derived based on the worst case assumption.

In case, not to make the worst case to be too extreme, the network mayassure the difference between two subframes in terms of power is limitedto a certain value such as A which can be configured by the network.Thus, a UE can add A as the potential power of the latter subframebetween two overlapped subframes. When the power is exceeded P_(CMAX) asthe network may assign higher power than A, the power in the lattersubframe may be reduced.

In addition, the following assumptions CD C) need to be assumed when theUE does not know the power of subframe k+1.

{circle around (a)} M_(PUSCH,c)(j) is the bandwidth of the PUSCHresource assignment expressed in number of resource blocks valid forsubframe j and serving cell c. For M_(PUSCH,c)(j), three alternativescan be considered. (i) Alt1: It can be assumed that M_(PUSCH,c)(j) isthe same as the previous subframe k. (ii) Alt2: M_(PUSCH,c)(j) can beassumed as the maximum value (assume that the UE is scheduled with theentire system bandwidth). (iii) Alt3: It can be assumed thatM_(PUSCH,c)(j) is delta+previous subframe k value (i.e., only delta willbe increased){circle around (b)} Other values are assumed to be the same as previoussubframe except power control adjustment factor f_(c)(i) which ischanged based on TPC. In this case, since the larger value is theimportant to account for, the maximum value configurable by TPC can beassumed (e.g., by accumulated TPC 3 dB and by absolute TPC of 4 dB).{circle around (c)} In terms of maximum power reduction (MPR) and otherparameters to determine P_(CMAX),c (k+1), a UE may assume the worstcondition to take the minimum MPR for carrier c (for MeNB).

In general, a UE can assume the potentially worst case of power insubframe (k+1).

When P_SeNB and P_MeNB are configured as ratio of P_(CMAX), as P_(CMAX)may change per subframe, not to look at the latter subframe, also theworst case assumption may be needed. One simple way is to use P_(CMAX)_(_) _(L,c) as for the baseline of computation such that P_SeNB andP_MeNB can be decided without look-ahead.

Currently, P_(CMAX) _(_) _(L,c) may be determined as equation 11.

P _(CMAX) _(_) _(L,c)=MIN {P _(EMAX,c) −T _(C,c) ,P_(Powerclass)−MAX(MPR _(c) +A-MPR _(c) +T _(IB,c) ,P−MPR _(c))−T_(C,c)}  <Equation 11>

Thus, using table 2, MPR may be assumed as 2 dB in worst case. Table 2defines an example of relationships between modulation, bandwidth andMPR.

TABLE 2 Channel bandwidth/Transmission bandwidth (N_(RB)) 1.4 3.0 5 1015 20 MPR Modulation MHz MHz MHz MHz MHz MHz (dB)QPSK >5 >4 >8 >12 >16 >18 ≦1 16 QAM ≦5 ≦4 ≦8 ≦12 ≦16 ≦18 ≦1 16QAM >5 >4 >8 >12 >16 >18 ≦2

When a UE supports non-contiguous UL (and the network may configurewhether it will use it or not at least in asynchronous case for MPRestimation), MPR can be CEIL{M_(A), 0.5} means rounding upwards toclosest 0.5 dB, i.e. MPRε[3.0, 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0].Thus, 8.0 dB can be assumed as the worst case.

Or, if the UE cannot do look-ahead, it can be assumed thatnon-contiguous transmission is not scheduled and thus MPR does not needto be accounted for.

MPR may be assumed to be known based on CA or DC band combination. Inthis case, MPR can be assumed as the worst value as well.

Tolerance T_(IB,c), can be assumed to be known as well. It can bedifferent based on P_(CMAX) as shown in table 3.

TABLE 3 P_(CMAX) (dBm) Tolerance T (P_(CMAX)) (dB)  21 ≦ P_(CMAX) ≦ 232.0  20 ≦ P_(CMAX) < 21 2.5  19 ≦ P_(CMAX) < 20 3.5  18 ≦ P_(CMAX) < 194.0  13 ≦ P_(CMAX) < 18 5.0  8 ≦ P_(CMAX) < 13 6.0 −40 ≦ P_(CMAX) < 87.0

Since, MPR can be determined by the UE, MPR can be fixed regardless ofsubframe. Yet, the worst case may be assumed. For example, the samevalue can be taken from the previous subframe.

Thus, though the actual value may change, in terms of computingP_(CMAX), the worst case may be assumed close to P_(CMAX,L) (or theworst of P_(CMAX,L)), then this value is used for computingP_SeNB/P_MeNB in case look-ahead is not feasible.

The worst case for P-MPR can be also assumed. And P_(CMAX,H,c) isdetermined as P_(CMAX) _(_) _(H,c)=MIN {P_(EMAX,c), P_(Powerclass)}

In case, look-ahead is not feasible, P_(CMAX,c2)(n) is computed as min{P_(CMAX)−P_(CMAX,c1)(k), P_(CMAX,c2)(n)}. In other words, the maximumpower usable for a carrier c2, is bounded by the power not used byprevious transmission. This would be very inefficient power usage.

So, a UE is not expected to exceed P_(powerclass) in any time, andP_(CMAX) is computed based on existing equation 12 and the power used byprevious subframe (or the same subframe or the subframe corresponding tothe same subframe).

P _(CMAX) _(_) _(L) _(_) _(CA)(n,k)=MIN {10 log₁₀ΣMIN [P _(EMAX,c)/(t_(C,c)),P _(PowerClass)/(mpr _(c) ·a-mpr _(c) ·t _(C,c) ·t _(IB,c)(n ork)),

P _(CMAX)(n,k)=min{P _(CMAX)(n,k),estimated_P _(CMAX)(n,k+1)}  <Equation12>

In equation 12, estimated_(—) P_(CMAX) is based on the worst caseassumption.

FIG. 14 briefly describes behavior of determining P_(CMAX).

In summary, for P_(CMAX) computation, when look-ahead is not feasible,we propose to assume the worst MPR related to MCS and not supportnon-contiguous UL transmission.

Particularly this may be applicable for intra-band non-contiguouscarriers are used between MeNB and SeNB uplink transmissions.Furthermore, it can be also considered to disable non-contiguous ULtransmission in dual connectivity (at least for asynchronous case wherethe overlap portion (smaller) is larger than X (e.g., 33 μs) or timingdifference between two uplink transmissions is larger than X (e.g., 33μs)).

Simple Computation Limited to One Subframe Pair

If look-ahead is not feasible, a UE may not take subframe (k+1) intoaccount for the computation. The next subframe will reduce the powerlower than P_(CMAX). In other words, power limited case always isdetermined based on subframe (n, k). To determine the overlappedsubframe for power computation and determining power limited case (todetermine “k” which is the overlapped subframe), a few mechanisms can beconsidered such as (a) to (e).

(a) k-th subframe is always the first overlapped subframe. (b) k-thsubframe is the subframe which has larger overlap portion between twooverlapped subframes. (c) k-th subframe is the second overlappedsubframe if the overlapped portion (smaller one) is less than X (e.g.,33 μs), otherwise, k-th subframe is the first overlapped subframe. (d)‘k’ is determined by offset configured by higher layer between MeNB andSeNB (e.g., k=n+offset). (e) It is up to UE to determine k

When k is decided for subframe n, this invention discusses how to applyP_SeNB and P_MeNB respectively. Using the previous diagram example,let's call P_(CMAX)(n, k) and P_(CMAX)(n, k+1) where P_(CMAX) (n, k+1)is determined by subframe n and subframe k+1.

When the ratio is given, for subframe n (SeNB), the Power to SeNB isdetermined by a few alternatives 1) to 5) (for example, P_SeNB=50%,P_MeNB=50%, P_(CMAX)(n,k)=22, P_(CMAX)(n−1, k)=21, P_(CMAX)(n, k+1)=21).

1) Power_SeNB=min {P_(CMAX)(n, k)*P_SeNB, P_(CMAX) (n−1, k)*P_SeNB}

Since P_(CMAX)(n−1, k) may be smaller than P_(CMAX)(n,k), it can takethe minimum between the two—This would not interfere with powerallocated to MeNB in subframe k−1.

2) Power_SeNB=max {P_(CMAX)(n, k)*P_SeNB, P_(CMAX)(n−1, k)*P_SeNB}

This may interfere with power allocated to MeNB, since this may notguarantee the UE power less than P_(CMAX) always. Thus, this needs beused with some relaxation of UE maximum power (such as less thanP_(powerclass))

3) Power_SeNB=P_(CMAX)(n,k)*P_SeNB

Similar to 2), this would cause some power issue.

4) Power_SeNB=min(P_(CMAX)−PowerUsedbyMeNB(n−1, P_(CMAX)(n,k)*P_SeNB)

To address the issue of previously allocated power to MeNB, anotherapproach is to take minimum between (unused power by MeNB in previoussubframe and power applicable to SeNB in this subframe)

5) At least for inter-band carriers, Power_SeNB=sum (P_(CMAX,cci)(n,k))−3 dB can be used where cci is the carriers belonging to SeNB. Thisassumes that MeNB and SeNB equally partition the maximum power andP_(CMAX) is affected by P_(CMAX,c) equally.

The similar mechanism is applicable to Power_MeNB as well.

One more clarification regarding Power_SeNB or Power_MeNB is that it canbe updated as

Power_xeNB=min{Power_xeNB (computed by one of the above), sum(P_(EMAX),c)} for carriers belong to xeNB. Here, P_(EMAX,c) is a maximumuplink transmission power per a cell. In other words, if P_(EMAX) isconfigured low, the total power can be adjusted accordingly. This wouldbe useful to compute the remaining power.

Or, it can be also considered not to configure dual connectivity in theallowed power reduction i.e. additional MPR (A-MPR) applicable scenariowith intra-band non-contiguous carriers assigned to MeNB and SeNB. Inother words, if there is A-MPR needs to be considered between MeNB andSeNB for asynchronous case, not to complicate the computation, UE mayreport that dual connectivity is not supported for that carriers atleast for asynchronous case.

Thus, a UE may report dual connectivity capability separately forsynchronous case and asynchronous case (or look-ahead and non-look-aheadcase) per band and band-combination.

Moreover, it can be also considered that intra-band contiguous ornon-contiguous carriers may not be used for asynchronous dualconnectivity case as it complicates the computation. In other words,only inter-band carriers can be utilized for dual connectivity scenarioat least for asynchronous case to minimize the impacts from MPR of theother eNB to one eNB power.

To minimize the impact, P_(EMAX,c) is configured such that P_(CMAX) _(_)_(L) is always lower than P_(CMAX) _(_) _(H) and also sum of P_(EMAX,c)with tolerance does not exceed power sum considering MPR. In otherwords, P_(CMAX) is derived based on MPR values only. In that case, atleast for inter-frequency carriers, P_(CMAX) change per subframe can belimited to P_(CMAX,c-L).

Or, it can be also considered to limit P_(EMAX) per each carrier to belower than P_(powerclass) 3 dB (if we assume only two uplink carriers).

When the small overlap portion is less than X (e.g., 33 μs), this may beapplied, or always take 3) (i.e. Power_SeNB=P_(CMAX)(n,k)*P_SeNB) aspower in the small overlap portion may be handled by UE implementation.

The same thing can be applied for MeNB computation. In this case,P_(CMAX,c)(k+1) is limited by P_(CMAX)(n,k+1)−P_(CMAX,c)(n). In otherwords, in terms of P_(CMAX), the power not used by subframe n can beused for subframe k+1, or, P_(CMAX)(n, k).

FIG. 15 briefly describes an example of handling limitation on the powerconsidering power used in previous subframe. Referring to FIG. 15, ifP_(CMAX)(n,k+1) is smaller than P_(CMAX)(n,k), the power applicable tosubframe (n+1) would be limited by P_(CMAX)(n,k+¹) and power used bysubframe n towards SeNB.

In summary, P_(CMAX) is computed at each subframe pair such as (n,k) andthe usable power can be limited to P_(CMAX)—used power in previoussubframe.

Thus, to handle power limited case, usable power is limited by theprevious subframe power usage. In summary, with P_SeNB/P_MeNB, the powerlimited case handles as follows a) to e).

a) At subframe (n, k) for SeNB transmission, compute Power_SeNB as oneof the candidate in the above.

b) At subframe (n,k) for MeNB transmission, computePower_MeNB=P_(CMAX)(n,k)*P_MeNB

c) If the allocated power does not exceed Power_SeNB, transmit.

d) Otherwise, compute the power unused by P_(CMAX)(n,k)—power used byMeNB at (n, k−1).

e) Use up to min {P_(CMAX,c), P_(CMAX)(n,k)−P_used_MeNB(n,k−1),P_(CMAX)(n,k)−Power_SeNB}

FIG. 16 is a flow chart briefly describing an example as for anoperation of the UE according to the present invention(s) in thisdisclosure. In the example of the FIG. 16, the operations are describedas performed by the UE in order to help to understand the invention(s)easily. However, the operation in this flow chart may be performed by aprocessor.

According to the FIG. 16, the UE may receive a signal on a downlinkchannel (S1610). Here, the signal may include information ontransmission power which indicates a power control mode.

The UE may determine whether primary cell (PCell) and secondary cell(SCell) are asynchronous or synchronous (S1620).

The UE may determine maximum transmission power for the SCell (S1630).Here, the UE may determine the maximum transmission power using theinformation on transmission power as well as the result of determinationon whether the PCell and the SCell are asynchronous or synchronous.

The subframe of the SCell may be overlapped with subframes of the PCellwhen the PCell and the SCell are asynchronous. In this case, powerheadroom for the subframe of the SCell can be determined based on one ofthe overlapped subframes of the PCell.

The details on determination for the maximum transmission power are sameas described with figures.

The UE may transmit signal to the SCell based on the maximumtransmission power for the SCell (S1640).

FIG. 17 is a block diagram which briefly describes a wirelesscommunication system including an UE 1700 and a BS (eNB) 1740. The UE1700 and the BS 1740 may operate based on the description as explainedabove.

In view of downlink, a transmitter may be a part of the BS 1740 and areceiver may be a part of the UE 1700. In view of uplink, a transmittermay be a part of the UE 1700 and a receiver may be a part of the BS1740.

Referring to FIG. 17, the UE 1700 may include a processor 1710, a radiofrequency (RF) unit 1720, and a memory 1730.

The processor 1710 may be configured to implement proposed proceduresand/or methods described in this application. For example, the processor1710 operatively coupled to the RF unit 1720 and the memory 1730. Theprocessor 1710 is configured for transmitting/receiving signals via theRF unit 1720 based on a scheduling for UL and/or DL.

The processor 1710 may determine whether primary cell (PCell) andsecondary cell (SCell) are asynchronous or synchronous. The processor1710 may determine maximum transmission power for the SCell using theinformation on transmission power as well as the result of determinationon whether the PCell and the SCell are asynchronous or synchronous.

The RF unit 1720 may transmit and receive a radio signal withtransmission power allocated by the processor 1710. The RF unit 1720receives a signal on a downlink channel in dual connectivity with mastereNB (MeNB) and secondary eNB (SeNB).

The memory 1730 is coupled with the processor 1710 and stores a varietyof information to operate the processor 1710.

The details on the operation of processor 1710, RF unit 1720, memory1730 are same as describe before.

The BS 1740 may include a processor 1750, a radio frequency (RF) unit1760, and a memory 1770.

The processor 1750 may be configured to implement proposed proceduresand/or methods described in this application. For example, the processor1750 operatively coupled to the RF unit 1760 and the memory 1770. Theprocessor 1750 is configured for transmitting/receiving signals via theRF unit 1760 based on a scheduling for UL and/or DL.

The processor 1750 may schedule UL and/or DL and may transmit signalincluding information on uplink transmission power which can be used inthe UE 1710. The received signal from the UE may be transmitted usingthe transmission power determined by the UE based on the information.Explains on this was provided before.

The RF unit 1760 may transmit and receive a radio signal, whereintransmission power for the received radio signal was allocated by the UE1700 as explained. The RF unit 1760 receives a signal on a downlinkchannel in dual connectivity.

The memory 1770 is coupled with the processor 1750 and stores a varietyof information to operate the processor 1750.

In the above exemplary systems, although the methods have been describedon the basis of the flowcharts using a series of the steps or blocks,the present invention is not limited to the sequence of the steps, andsome of the steps may be performed at different sequences from theremaining steps or may be performed simultaneously with the remainingsteps.

Furthermore, the above-described embodiments include various aspects ofexamples. Accordingly, the present invention should be construed toinclude all other alternations, modifications, and changes which fallwithin the scope of the claims.

In the description regarding the present invention, when it is said thatone element is “connected” or “coupled” to the other element, the oneelement may be directly connected or coupled to the other element, butit should be understood that a third element may exist between the twoelements. In contrast, when it is said that one element is “directlyconnected” or “directly coupled” to the other element, it should beunderstood that a third element does not exist between the two elements.

What is claimed is:
 1. A method of controlling an uplink transmissionpower, by a user equipment (UE), in a wireless communication system, themethod comprising: receiving an indication of a power control mode via ahigher layer from a master eNodeB (eNB) in dual connectivity;determining whether the MeNB and a secondary eNB (SeNB) in dualconnectivity are asynchronous or synchronous with each other based on atiming difference between the MeNB and the SeNB; determining atransmission power for the SeNB based on the indication of the powercontrol mode and whether the MeNB and the SeNB are asynchronous orsynchronous; and transmitting an uplink signal to the SeNB based on thetransmission power for the SeNB.
 2. The method of claim 1, furthercomprising transmitting a UE capability on whether the UE supports anasynchronous dual connectivity or not to the eNB.
 3. The method of claim2, wherein the UE capability indicates that the UE does not support theasynchronous dual connectivity.
 4. The method of claim 3, wherein theindication of the power control mode indicates a power control mode forsynchronous dual connectivity.
 5. The method of claim 2, wherein the UEcapability indicates that the UE supports the asynchronous dualconnectivity.
 6. The method of claim 5, wherein the indication of thepower control mode indicates a power control mode for synchronous dualconnectivity or a power control mode for asynchronous dual connectivity.7. The method of claim 1, wherein the MeNB and the SeNB are synchronouswith each other when the timing difference between the MeNB and the SeNBis equal or less than a predetermined threshold value.
 8. The method ofclaim 1, wherein the MeNB and the SeNB are asynchronous with each otherwhen the timing difference between the MeNB and the SeNB is larger thana predetermined threshold value.
 9. A user equipment (UE) in a wirelesscommunication system, the UE comprising: a memory; a radio frequency(RF) unit; and a processor, coupled to the memory and the RF unit, that:controls the RF unit to receive an indication of a power control modevia a higher layer from a master eNodeB (eNB) in dual connectivity,determines whether the MeNB and a secondary eNB (SeNB) in dualconnectivity are asynchronous or synchronous with each other based on atiming difference between the MeNB and the SeNB, determines atransmission power for the SeNB based on the indication of the powercontrol mode and whether the MeNB and the SeNB are asynchronous orsynchronous, and controls the RF unit to transmit an uplink signal tothe SeNB based on the transmission power for the SeNB.
 10. The method ofclaim 9, wherein the processor further controls the RF unit to transmita UE capability on whether the UE supports an asynchronous dualconnectivity or not to the eNB.
 11. The method of claim 10, wherein theUE capability indicates that the UE does not support the asynchronousdual connectivity.
 12. The method of claim 11, wherein the indication ofthe power control mode indicates a power control mode for synchronousdual connectivity.
 13. The method of claim 10, wherein the UE capabilityindicates that the UE supports the asynchronous dual connectivity. 14.The method of claim 13, wherein the indication of the power control modeindicates a power control mode for synchronous dual connectivity or apower control mode for asynchronous dual connectivity.
 15. The method ofclaim 9, wherein the MeNB and the SeNB are synchronous with each otherwhen the timing difference between the MeNB and the SeNB is equal orless than a predetermined threshold value.
 16. The method of claim 9,wherein the MeNB and the SeNB are asynchronous with each other when thetiming difference between the MeNB and the SeNB is larger than apredetermined threshold value.